Summary of Option Activity (Detail) $ / shares in Units, shares in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Shares
Shares, Outstanding, Beginning Balance | shares	4.8
Shares, Granted | shares	0.5
Shares, Exercised | shares	(1.4)
Shares, Outstanding, Ending Balance | shares	3.9
Shares, Vested and expected to vest | shares	3.7
Shares, Exercisable | shares	2.8
Weighted Average Exercise Price
Weighted Average Exercise Price Per Share, Beginning Balance | $ / shares	$ 46.47
Weighted Average Exercise Price Per Share, Granted | $ / shares	81.02
Weighted Average Exercise Price Per Share, Exercised | $ / shares	50.1
Weighted Average Exercise Price Per Share, Ending Balance | $ / shares	49.68
Weighted Average Exercise Price Per Share, Vested and expected to vest | $ / shares	48.81
Weighted Average Exercise Price Per Share, Exercisable | $ / shares	$ 38.68
Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term, Outstanding	4 years 6 months
Weighted Average Remaining Contractual Term, Vested and expected to vest	4 years 4 months 24 days
Weighted Average Remaining Contractual Term	3 years 2 months 12 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding | $	$ 172.2
Aggregate Intrinsic Value, Vested and expected to vest | $	171
Aggregate Intrinsic Value, Exercisable | $	$ 157.6